It is of course well known to those skilled in the art of facsimile apparatus that all transmissions are standardized so that facsimile machines around the world can communicate with each other. It is necessary for all facsimile machines to convert information which is to be sent, into standard coded information which can be decoded by the proper facsimile machine when it is received.
The CCITT, which is an international telecommunications group, has set the standards for the various facsimile apparatus groups. At present, group 3 (G3) is the most important group since most facsimile apparatus falls within this group. Group 3 includes modified Huffman (MH) coding and modified Read (MR) coding.
In prior art facsimile machines, the compression or coding is accomplished by following a software procedure in a relatively standard, dedicated CPU, or microprocessor. The expansion or decoding is accomplished by following a substantially reverse software procedure in the same CPU or microprocessor.
The major problem with the prior art software procedures is that they are extremely complicated to write and difficult to incorporate into CPUs or microprocessors. Also, the software procedures can only perform one step at a time instead of allowing several related steps to occur simultaneously. Thus, the clock frequencies of the software processes must be very high to get the desired speed. Also, a dedicated CPU is used so that the actual hardware becomes relatively expensive.